Wakeboat draft measuring system and methods

ABSTRACT

Wakeboat hull control systems and methods are provided to permit the accurate reproduction of a wake behind a wakeboat. The onboard wake control system receives data from a draft measuring system. Incorporation of the data from the draft measuring system permits accurate reproduction of a wake behind the wakeboat after a change in an onboard variable such as the number, weight or position of passengers, the weight or position of cargo and the position of trim tabs or amount/location of ballast.

CROSS RELATED

This application claims the benefit of previously filed U.S. ProvisionalApplication Ser. No. 62/201,030 filed on Aug. 4, 2015.

BACKGROUND

Watersports involving powered watercraft have enjoyed a long history.Recently, watersports have emerged which are conducted in theintentionally enhanced wake of a watercraft. Such pursuits arecollectively referred to as “wakesports” and include wakeboarding,wakesurfing, and wakeskating. The specialized boats used to create theenhanced wakes associated with wakesports are referred to in theindustry as “wakeboats”.

Wakeboats create their enhanced wakes using a variety of techniques. Theprimary cause of a boat's wake is the displacement of water by its hull.Changes to the hull's orientation in the surrounding water directlyaffect the size, shape, and perceived quality of the resulting wake. Aswakesports have become more popular, many different techniques have beendeveloped to alter the orientation of a wakeboat's hull in the water andthus change the nature of the wake it produces.

When optimizing the wake for a particular watersports participant, andespecially when seeking to reproduce wake conditions achieved at sometime in the past, the entire relationship between the hull and the bodyof water in which it is moving must be taken into account. As notedabove, the behavior of the wake is primarily controlled by how the hulldisplaces the water, which is in turn controlled by the draft and anglesof the wakeboat hull in the water. When a preferred wake has beenachieved through careful arrangement of such factors as ballast amountsand trim tab settings, it is very desirable to “store” the hullconditions which resulted in the preferred wake behavior. Ideally, thesame preferred wake could then be reproduced by recalling the storedconditions and duplicating them.

Some existing wake enhancement systems attempt to provide such a “storeand recall” feature. One common approach is to remember the amount ofballast in various ballast chambers situated around the boat, on thepremise that if the same amount of ballast is later restored to thosecompartments the attitude of the hull will be duplicated and thepreferred wake duplicated as well.

The reality is not so simple. Hull attitude is affected by many factorsbeyond just ballast amounts, including but in no way limited to theamount of fuel onboard, the amount of equipment onboard, the number ofpassengers onboard, and the relative weight and positioning of all ofthese variables. Worse, these factors can and do change in real timesuch as when passengers embark and disembark or move around within thewakeboat, or fuel is consumed or refilled during a day's operation.

Compounding these realities is the fact that boating in general, andwatersports in particular, are often very social events. Passengers comeand go during a single outing. Even changing the current watersportparticipant (say, from a heavier to a lighter wakeboarder) alters theamount and distribution of weight in the hull. All of this may involvesmall children to large adults. These very natural occurrences causemulti-hundred pound changes in weight distribution, correspondingsubstantial changes in hull angles and draft, and thus significantvariability in the wake produced.

Wake control systems flatly ignore such changes and the effects theyhave on hull orientation. By relying on the fiction that identicalballast and trim tab settings will yield an identical relationshipbetween hull and water, they fail to measure and/or accommodate for thesubstantial effects of day to day, and sometimes minute to minute,changes in equipment and passengers on board the wakeboat. Thesedeficiencies can lead to significant frustration of wakeboat owners,angry customer service calls to wakeboat dealers, and damage to thereputation of wakeboat manufacturers.

More recently, advanced wake control systems have finally recognized theneed to measure and control the actual hull of the wakeboat. Instead ofmistakenly focusing on accessories such as ballast and trim tabs, theseadvanced systems measure the actual relationship of the hull to thesurrounding water and then adjust the ballast, trim tabs, and otheraccessories to restore the hull to the same conditions. One such systemis described in U.S. Pat. No. 8,798,825 issued Aug. 5, 2014, theentirety of which is incorporated by reference herein.

SUMMARY OF THE DISCLOSURE

Disclosed herein is a wake control system for use on a wakeboat. Thesystem comprises a wakeboat having a hull, at least one trim tabattached to the wakeboat, at least one ballast tank carried by thewakeboat and an onboard wake control system suitable for controlling theposition of the trim tab and fluid levels within the ballast tank. Theonboard wake control system including memory sufficient to store dataassociate with the position of the trim tab and fluid level within theballast tank. The hull of the wakeboat has a hole positioned below theoperational water line. Positioned within the hold is a fitting andattached to the fitting is an open pipe providing fluid communicationbetween the exterior and interior of the hull. The pipe carries a draftmeasuring system capable of generating a signal representative of a wakeprofile of the hull within the water. The signal generated by the draftmeasuring system is received and stored within the wake control system.

Also disclosed herein is a method for accurately reproducing a wakebehind a wakeboat. The method comprises the steps of providing awakeboat having a hull fitted with a draft measuring system. Thewakeboat further includes at least one trim tab and at least one ballasttank controlled by an onboard wake control system. A first wake isestablished behind the wakeboat. Upon establishing the desired wake, thedraft of the hull is measured by the use of a draft measuring system.The draft measuring system then transmits a signal representative of thedraft of the hull to the onboard wake control system which stores thevalue of the measured draft. Subsequently, changes are made in commonvariables on the wakeboat, including but not limited to, number ofpassengers on the wakeboat, position of the passengers on the wakeboat,weight of all passengers on the wakeboat, weight of cargo and/orposition of cargo on the wakeboat, the angle of the at least one trimtab and/or the fluid level within the at least one ballast tank.Following the change in the one or more variables, the use of the draftmeasuring system and wake control system will reproduce the stored firstwake.

DRAWINGS

Embodiments of the disclosure are described below with reference to thefollowing accompanying drawings.

FIG. 1 is a cutaway view of the hull of a watercraft illustrating howone embodiment of the present disclosure makes the level of the watersurrounding the hull available for measurement within the hull.

FIG. 2 illustrates one embodiment of the present disclosure depictingmechanical measurement of hull draft.

FIG. 3 illustrates one embodiment of the present disclosure depictingoptical measurement of hull draft.

FIG. 4 illustrates one type of filtering used in some embodiments of thepresent disclosure.

FIG. 5 illustrates one embodiment of the present disclosure depictingultrasonic measurement of hull draft.

FIG. 6 illustrates one embodiment of the present disclosure depictingair pressure measurement of hull draft.

FIG. 7 illustrates one embodiment of the present disclosure depictingcapacitive measurement of hull draft.

FIG. 8 illustrates one example of how capacitive strip shape affects theresulting relationship between hull draft and capacitance.

FIG. 9 illustrates another example of how capacitive strip shape affectsthe resulting relationship between hull draft and capacitance.

DESCRIPTION

This disclosure is submitted in furtherance of the constitutionalpurposes of the U.S. Patent Laws “to promote the progress of science anduseful arts” (Article 1, Section 8).

One of the important parameters associated with the hull's relationshipto the surrounding water is its depth in that water. The proper term forthat measurement is “nautical draft” or just “draft”, whichdifferentiates it from the depth of the water itself (from the water'ssurface to the “land” lying beneath the body of water). Draft is one ofthe significant degrees of freedom for a hull, and any wake controlsystem which seeks to measure and manage the hull of its wakeboat mustmeasure and manage draft.

A simply scenario will serve to illustrate the importance of draft to awakeboat and wakesports. On a given day, suppose that a wakeboat has onewakesports participant in the wake behind the boat and three adultpassengers onboard watching and/or coaching. The participant likes thewake configuration and asks that it be stored in memory by the boat'swake control system for recall in the future.

On a subsequent day, the same wakesports participant now has six adultpassengers onboard instead of three. The previously stored wakeconfiguration is recalled, which causes duplication of the ballastamounts, trim tab angles, hull speed, and other factors. However,despite the representation of the wake control system that the storedconditions have been reproduced, the truth is quite different. In fact,the hull's conditions have not been reproduced: There are three moreadult passengers in the boat than when the parameters were originallystored. If those passengers average 160 pounds each, they have added 480pounds.

This additional weight will cause the hull to sink lower into thesurrounding water. In nautical terms, the watercraft's draft willincrease as the hull increases its wetted surface to achieve equilibriumwith its increased load. As previously explained, the behavior of thewake is primarily controlled by how the hull displaces the water—and nowthe hull is displacing significantly more water due to the increasedweight of the additional passengers. Just three passengers representnearly 500 pounds—a very large weight change in the context ofwakesports, one that will have a very dramatic effect on the nature andquality of the wake produced behind the wakeboat.

It is clear that to restore a previous wake configuration, a wakecontrol system must compensate for changes such as different passengerload. A modern, proper, and advanced wake control system would adjustthe ballast or trim tab angles based on actual hull measurements andchange the amount of ballast or angles of trim tabs—not to make themequal with some previous values (by mistakenly focusing on hullaccessories), but to put the hull back where it belongs (by properlyfocusing on the hull itself).

In the scenario above, restoring the hull's former buoyancy wouldrequire a reduction in ballast to offset the additional weight of thethree extra passengers. Sometimes changes may require more ballast ortrim tab angles; other times they may require less. What matters is thehull, not the accessories.

Therefore, to actually duplicate an earlier wake, a proper wake controlsystem must measure what the hull is actually doing. As is clear fromthe description above, measuring ballast amounts or trim tab angles orother secondary characteristics does not capture all of the factorsaffecting the hull. Even manually entering passenger count, or weight,or seating arrangement, is insufficient because passengers are not theonly variable. The hull is what matters. The hull itself must bemeasured, and as the preceding example proves, the hull's depth in thewater—its draft—is an important component of both measuring a hull andrestoring that hull to the same relationship with the surrounding water.

The purpose of a nautical draft sensor is to measure the depth of awatercraft's hull in the surrounding water; i.e. how “deep” the hullsinks into the water at any given time. Generally speaking, a primarypurpose of a watercraft's hull is to keep the water on the outside ofthe boat. This puts the hull at odds with the desire to measure thehull's depth in the water, because under most circumstances the hullintentionally isolates equipment, including sensors that are within thehull from the water outside of the hull.

Embodiments of the present disclosure rely on the behavior of water to“seek its own level”. The present disclosure provides draft measuringsystems that measure the water level—and thus the hull's draft—fromwithin the hull without directly contacting the water itself andtransmit a signal representative of the measured draft to an onboardwake control system. The results include significant advantages ofsafety, reliability, and flexibility of sensor design and installation.

FIG. 1 illustrates one portion of a watercraft hull. Hull 1 is of aV-shaped design, one of many popular styles used in the marine industry.The use of a V-shaped hull in FIG. 1 is for convenience and not intendedto limit the applicability of the present disclosure, which iscompatible with virtually any style or shape of hull.

Continuing with FIG. 1, hull 1 is provided with an opening 2 in which afitting 3 is installed. Fitting 3 may be, for example, a “mushroom”style such as a THMR1.000-B that protrudes beyond the natural hullprofile (Marine Hardware, 14560 NE 9151 Street, Redmond, Wash. 98052); a“seacock” style such as a SEAC1.000-B that contains an integrated valve(Marine Hardware, same); a “flush mount” style that does not disrupt thenatural provide of the exterior of the hull such as a 0331 006PLB (PerkInc., 16490 NW 131 Avenue, Miami, Fla. 33169); or another style whosecharacteristics suit the specific application.

If the selected fitting does not include an integrated shutoff, a valve4 such as a BVLV1.000-FPHL (Marine Hardware, 14560 NE 91st Street,Redmond Wash. 98052), or another valve whose characteristics suit thespecific application, may be included as a safety measure to permitclosure of the hull opening if necessary.

In some embodiments of the present disclosure, the bottom of a pipe 5 isattached to the top of fitting 3 (or valve 4, if present) as shown. Thetop of pipe 5 is open to the ambient environment. When valve 4 is eitherabsent or open, water is able to flow in and out of pipe 5 throughfitting 3. Due to the well known behavior of water to “seek its ownlevel”, the level 6 of the water in pipe 5 will seek the same level asthe level 7 of the water outside of hull 1. For clarity, the dashed linelabeled “common level” in FIG. 1 highlights this relationship betweenthe water levels inside and outside of the hull.

This coordination of levels will continue even as the level 7 of thewater outside of hull 1 changes. As hull 1 sits or moves deeper in thesurrounding water, the outside water level 7 will rise and the level 6of the water in pipe 5 will rise accordingly. Likewise, as hull 1 risesor moves shallower in the surrounding water, the outside water level 7will fall and the level 6 of the water in pipe 5 will drop accordingly.

FIG. 1 illustrates pipe 5 at an angle due to the angle of hull 1. Thehydraulic behavior of the water level in pipe 5 is tolerant ofsignificant angles and in most cases there is no need to “straighten”pipe 5 towards vertical. One advantageous benefit of this characteristicis that the present disclosure is operable even if hull 1 is tilted at asignificant angle during watercraft operation, a condition commonlyencountered while engaged in wakesports activities. However, if suitablefor a specific application, an angularly articulated fitting could beused between fitting 3, valve 4, and/or pipe 5 to orient pipe 5 asdesired to permit repositioning and/or reorientation of pipe 5 from thatotherwise imposed by opening 2 or hull 1.

This portion of the present invention can combine economical componentsfamiliar to the marine industry to make the surrounding water levelavailable within the hull of a watercraft, in the form of a water column8 whose height is directly proportional to the draft of the watercraft'shull. Measuring the height of water column 8 within the hull thenindicates the “depth”, or draft, of the hull in the surrounding water.

The following disclosures of the present invention present manytechniques for measuring the height of water column 8.

For convenience, FIG. 2 uses a vertical orientation (though, as notedabove, such an orientation is not required). Optional valve 4 is againconnected to pipe 5, in which water column 8 rises and falls with thedraft of the hull as described above.

In some embodiments, the present disclosure comprises a float mechanism9 that directly measures the height of water column 8. A buoyant float10 attached to float mechanism 9 via mechanical connection 11 sits onthe surface 6 of water column 8. As the top surface of water column 8rises and falls, so too does float 10, which communicates such physicalchanges to float mechanism 9 via connection 11. Float mechanism 9converts the level of float 10 to an output signal.

While embodiments based on FIG. 2 are functional, improvements arepossible. For example, in FIG. 2 at least some portion of the sensorcomponents are in direct contact with the water being measured. This mayexpose the sensor to debris or corrosion, especially in a salt waterenvironment, and thus require maintenance.

It would be a further advancement of the art to measure the draft of thehull while keeping the sensor entirely out of contact with the waterbeing measured.

FIG. 3 illustrates one such embodiment of the present disclosure. Inthis embodiment, pipe 5 is comprised of a generally opticallytransparent material such as clear polyvinyl chloride, popularly knownas PVC (product number 34134 from United States Plastic Corporation,1390 Neubrecht Road, Lima Ohio 45801) or another material whosecharacteristics suit the specific application.

In some embodiments, a buoyant float 12 sits on the surface 6 of watercolumn 8, but is otherwise allowed to move freely within, and requiresno connection to anything outside of, pipe 5. Constrictions at the endsof pipe 5 retain float 12 from exiting pipe 5.

Continuing with FIG. 3, an optical sensor 13 is attached to the outsideof pipe 5. In some embodiments, optical sensor 13 operates on theprinciple of transmission: One or more optical emitters, such as lightemitting diodes, transmit light through pipe 5 and the air or waterwithin and the light is sensed on the opposite side of pipe 5 by one ormore light-sensitive, wavelength compatible receptors such asphotodiodes or phototransistors. In other embodiments, optical sensor 13operates on the principle of reflection: One or more optical emitterstransmit light into pipe 5 and the reflection of the light is sensed onthe same side of pipe 5 by one or more light-sensitive, wavelengthcompatible receptors.

Optical sensor 13 may comprise, for example, an array of integratedsensors such as the IS31SE5000 (Integrated Silicon SolutionIncorporated, 1623 Buckeye Drive, Milpitas Calif. 95035) or anothersensor whose characteristics suit the specific application, togetherwith supporting circuitry.

In some embodiments, optical sensor 13 is able to sense the presence orabsence of water directly, by detecting changes in color or refractionor another figure of merit. As the height of water column 8 varies,optical sensor 13 directly detects its top surface and converts itsposition to an output signal.

In other embodiments, float 12 is optically compatible with opticalsensor 13 and pipe 5 such that optical sensor 13 can detect the positionof float 12 through pipe 5 via float 12's opaqueness (in a transmissiveembodiment) or reflectivity (in a reflective embodiment). As the heightof water column 8 varies, the position of float 12 varies with it.Optical sensor 13 detects the position of float 12 and converts thatposition to an output signal.

The embodiment of the present disclosure shown in FIG. 3 is asignificant improvement upon that shown in FIG. 2. The embodiment ofFIG. 3 isolates the water column 8 from optical sensor 13 on the outsideof pipe 5. The sensor is thus not exposed to debris, contamination, orcorrosion. The sensor also need not be tolerant of submersion, anenormous advantage which yields benefits in economy and manufacturing.

Another improvement delivered by some embodiments of the presentdisclosure accommodates the realities of open water. The watersurrounding the hull of a watercraft is often not calm, with undulationsand disturbances that cause the hull to rock and shift. Such movementsdo not represent changes in the average hull draft, but nevertheless cancause the height of water column 8 in pipe 5 to oscillate around theaverage hull draft.

The present disclosure can optionally incorporate filtering to reducesuch effects. One filtering technique, used by some embodiments, is toinstall a cap 14 or other sealed covering on pipe 5 as shown in FIG. 4.(Water level sensors are omitted from FIG. 4 for clarity.) Placing cap14 on pipe 5 could affect the ability of water to flow freely into andout of the bottom of pipe 5 due to the compression and rarification ofthe air 16 thus trapped at the top of pipe 5. Therefore, in someembodiments, cap 14 includes a vent 15 that permits the transfer of airat the top of pipe 5.

The diameter, shape, and other characteristics of vent 15 control therate at which air may transfer. A smaller vent imposes a greaterrestriction on the rate of transfer, which in turn imposes greaterrestriction on the rate at which the height of water column 8 canchange. The result is a mechanical low pass filter that imposes adamping effect on the oscillations of water column 8 and is just one ofmany techniques for mechanical filtering made possible by the presentdisclosure.

An additional benefit of vent 15 in cap 14 is a hard physical limit onthe rate at which the water surrounding the hull can inadvertently enterthrough the draft sensor, should the surrounding water level ever exceedthe top of pipe 5.

Some embodiments incorporate filtering at the electronic level withinthe sensor, such as float mechanism 9 of FIG. 2 or optical sensor 13 ofFIG. 3, or within the wake control system or other electronic system towhich the present invention is connected. For example, a passive RCfilter could be employed using off-the-shelf capacitors and resistorscommon in the electronics industry. An active filter based on anoperational amplifier such as a TLV2471 (Texas Instruments Inc., 12500T1 Boulevard, Dallas Tex. 75243), or another device whosecharacteristics suit the specifics of the application, could also beused.

Software filtering presents another option in some embodiments of thepresent disclosure. If the sensor comprises software or firmware, and/oris connected to a system comprising software or firmware, the signalcould be filtered using any of a wide variety of com man softwaretechniques.

All of these filtering approaches are well known to those skilled in theart and may be used individually, or in combination, as suitable for thespecific application. Filtering can also optionally be used to introduceintentional nonlinearities into the response of the draft sensor ifuseful or desirable.

Another sensing method, used by some embodiments, can include anultrasonic transducer that measures the distance from itself to anotherobject—in the present disclosure, the top of water column 8. Referringto FIG. 5, ultrasonic transducer 17 is attached to the top of pipe 5.The ultrasonic transducer may be, for example, one of the XL-MaxSonarWR/WRC series (MaxBotix Incorporated, 13860 Shawkia Drive, BrainerdMinn. 56401) or another device that suits the specifics of theapplication. Vent 15 is optionally present and incorporated intoultrasonic transducer 17, in the side near the top of pipe 5 asillustrated, or another location as suitable for the application.

Ultrasonic transducer 17 measures the distance from itself to the top ofwater column 8 to determine hull draft. As the height of water column 8rises with increasing hull draft, its surface draws nearer to ultrasonictransducer 17. Likewise, as the height of water column 8 falls withdecreasing hull draft, its surface recedes from ultrasonic transducer17.

A further enhancement, delivered by some embodiments of the presentdisclosure, uses the air trapped by the addition of cap 14 to advantage.Referring to FIG. 6, cap 14 is in place atop pipe 5. A pressuretransducer 18 is connected to vent 15 in cap 14, such that pressuretransducer 18 can measure the air pressure at the top of pipe 5.Pressure transducer 18 could be, for example, an MPXHZ6400A (FreescaleSemiconductor, 1300 North Alma School Road, Chandler Ariz. 85224) oranother device whose characteristics suit the specific application.

As the height of water column 8 increases (due to increased hull draft),the volume occupied by air 16 trapped in the top of pipe 5 will bereduced, resulting in compression and an increase in air pressure.Likewise, as the height of water column 8 decreases (due to decreasedhull draft), the volume occupied by air 16 will be increased, resultingin and a decrease in air pressure. Since gases (here, air 16) arecompressible and liquids (here, water column 8) are not, all of thepressure changes are experienced by air 16. Pressure changes to air 16therefore indicate the draft of the hull by indicating the height ofwater column 8. Pressure transducer 18 measures the pressure of air 16and, thus, the draft of the hull.

Embodiments of the present disclosure based on that shown in FIG. 6 makeit possible to preserve the benefits of the present disclosure'sinnovations while optionally locating the actual sensor at a remotelocation. For example, pressure transducer 18 could be connected to cap14 using hose or tubing. Such an arrangement could allow the purelymechanical components of the present disclosure to be located for theirbest function and advantage, while the potentially more sensitivepressure transducer 18 could be located in a location more suited to itsenvironmental requirements. This is not meant to imply that anyparticular type of transducer is overly sensitive. Instead, theflexibility to optionally locate the transducer away from water column 8itself represents yet another advantage of the present disclosure.

FIG. 7 illustrates yet another advancement delivered by some embodimentsof the present disclosure. Once again valve 4 is connected to pipe 5,allowing the surrounding water to flow in and out of pipe 5. Pipe 5 maybe comprised of almost any nonconductive material, for exampletraditional polyvinyl chloride (PVC) pipe (JM Eagle, 5200 West CenturyBoulevard, Los Angeles Calif. 90045) or another material whosecharacteristics suit the specific application.

Attached to the outside surface of pipe 5, and running substantiallyalong its length, are two conductive strips 19 and 20. These strips canbe virtually any conductive material, such as metalized Mylar or anothermaterial whose characteristics suit the specific application. Strips 19and 20 may be attached to pipe 5 using self-adhesive, or held in placeby heat shrink tubing, or another attachment technique as suits thespecific application. Strips 19 and 20 are installed on opposing sidesof pipe 5 and do not contact each other.

In operation, strips 19 and 20 form two plates of a capacitor. Watercolumn 8 acts as a variable dielectric between the capacitor platesformed by strips 19 and 20. As the height of water column 8 within pipe5 increases and decreases with changes to the hull draft, strips 19 and20 on the outside of pipe 5 experience increases and decreases in theamount of water present between them. Since water column 8 is acting asa dielectric in the capacitor formed by strips 19 and 20, the varyingdielectric causes a varying capacitance across strips 19 and 20.

It is important to note that water column 8 is on the inside of pipe 5while strips 19 and 20 are on the outside of pipe 5. The water does notcontact the strips, instead the water is sensed by the strips throughthe wall of the pipe. FIG. 7 includes a top view for clarity.

This embodiment of the present disclosure thus creates a variablecapacitor whose value is determined by the height of water column 8—or,stated more directly, a variable capacitor whose value indicates thedraft of the hull in the surrounding water.

A conversion module 21, electrically connected to strips 19 and 20,converts this varying capacitance to a signal that is compatible withthe wake control systems on modern wakeboats. Conversion module 21 maybe mounted to the top of pipe 5 as shown, or in any other suitablelocation compatible with the application. Conversion module 21 caninclude any of the well-known techniques for converting a capacitancevalue to a signal; as just one example, a frequency-to-voltage circuitwhose oscillation frequency is set by the capacitance in question. Itmay also comprise an off-the-shelf capacitance-to-voltage module (NewProvidence Systems, PO Box 2272, Pocatello Id. 83206) or another devicewhose characteristics suit the specific application.

Embodiments of the present disclosure based on that shown in FIG. 7deliver substantial advantages over existing draft sensors. They areeconomical, an important consideration in the competitive wakeboatindustry. They are rugged and reliable, with no moving parts and nomaintenance. Their fabrication can be outsourced to an external vendor,or accomplished in the same factory as the watercraft themselves byemployees possessing traditional skills using traditional tools. Theycan be fabricated and installed primarily using components alreadyfamiliar to, and commonly used in, the wakeboat industry. If installedwith a valve, they can be removed and replaced while the watercraftremains in the water using traditional tools. They are physicallycompatible with any current or future hull material. They areelectrically compatible with modern wake control systems and can be madecompatible with the signal requirements of future wake control systems.Embodiments of the present disclosure such as that shown in FIG. 7represent significant advancements in the art.

As with other embodiments of the present disclosure, those based oncapacitance sensing as illustrated in FIG. 7 can take advantage of themechanical, electrical, software, and firmware filtering techniquesdescribed above as suited to the specifics of a given application.

Additional adaptability may be realized by adjusting strips 19 and 20 inlength, width, and positioning to suit a given application. The minimumand maximum capacitance values from such embodiments of the presentdisclosure are related to such parameters as the surface area of strips19 and 20, and the material and diameter and length and wall thicknessof pipe 5. Given a preferred choice of characteristics for othercomponents, the length and width and positioning of strips 19 and 20 canbe easily adjusted to yield the best range of capacitance values.

As one example, an embodiment of the present disclosure that benefitsfrom a shorter pipe 5 would thus place a restriction on the maximumlengths of strips 19 and 20. To offset this loss of surface area (andthus capacitance), the widths of strips 19 and 20 could be increasedaccordingly.

As the widths of strips 19 and 20 increase, their side edges will “wraparound” pipe 5 and begin to approach each other, leading to undesiredparasitic capacitance between the strips themselves. This difficulty iseasily ameliorated by increasing the diameter of pipe 5, thus causingthe combined widths of strips 19 and 20 to represent a smallerpercentage of pipe 5's total circumference and causing the edges ofstrips 19 and 20 to draw away from each other as larger pipe diametersare used and the circumferential spacing between strips 19 and 20increases accordingly.

As another example, an embodiment of the present disclosure that uses alonger pipe 5 would accommodate longer lengths of strips 19 and 20. As aresult, the widths of strips 19 and 20 could potentially be reduced.This in turn may enable the use of a smaller diameter pipe 5, ifdesired.

As yet another embodiment represented by the present disclosure, it ispossible to accommodate nonlinearities by shaping of strips 19 and 20.Presuming strips 19 and 20 are rectangular in shape, a linearrelationship will exist between the height of water column 8 and theresulting capacitance value because the combined “active” surface areaof strips 19 and 20 will increase or decrease linearly as water column 8increases or decreases in height. However, if hull shape or otherconsiderations cause a nonlinear relationship between the height ofwater column 8 and the actual draft of the hull, the widths of strips 19and 20 may be varied along their length to introduce intentionalnonlinearity of the draft sensor's response, which can then be combinedwith the undesirable nonlinearity to yield a linear response.

In some embodiments of the present disclosure, this ability can be usedwhen nonlinearity is desired, or even to achieve completely arbitraryresponse curves.

Consider strips 19 and 20 of FIG. 8, shown “flat” before installation onpipe 5 for clarity of illustration. Water column 8 is illustrated“between” the strips. As water column 8 rises, it increases the activesurface area 21 (shaded for clarity) of strips 19 and 20 in a linearmanner due to the rectangular shape of the strips. Expresseddifferently, doubling the height of water column 8 doubles activesurface area 21. In such embodiments, this results in a linearrelationship between the height of water column 8 and the capacitanceacross strips 19 and 20. The curve of graph 22 illustrates such a linear(straight-line) relationship.

Alternatively, consider strips 19 and 0 of FIG. 9 which taper fromnarrow at the bottom to wide at the top. The percentage of activesurface area 21 of strips 19 and 20 increases faster than the percentageincrease of water column 8's height as the latter rises. Stated anotherway, doubling the height of water column 8 more than doubles activesurface area 21. The curve of graph 23 illustrates the resulting,nonlinear relationship between height and capacitance—and, moreimportantly, between hull draft and capacitance.

From FIGS. 8 and 9 some embodiments of the present disclosure providethe ability to alter the response curve through simple reshaping ofstrips 19 and 20. Identical components can be shared between multipleversions of draft measuring systems, yet their response curves can bemade dramatically different as necessary by simple trimming of strips 19and 20 before their assembly to pipe 5. Such customization of responsecurves—known as “curve fitting” in the electronics and otherindustries—is at least one advantage of the present disclosure.

In fact, this customized curve fitting is not limited to justpre-assembly. Adjustment of strips 19 and 20 can be performed afterassembly, during in-hull testing, or even as in-the-field calibrationfor especially precise applications. Strips 19 and 20 can be fabricatedof metalized Mylar, metallic foil, or other materials that allowtrimming to shape after application, with the undesired material thenpeeled away or otherwise removed. This allows some embodiments to becalibrated after assembly and installation into their final points ofuse—yet another dramatic and substantial advancement of the art.

The present disclosure supports a variety of output signal types. Insome embodiments, the output signal may be an analog voltage whichduplicates that of one or more traditional marine draft sensors.Alternatively, an analog voltage may be produced to be compatible with agiven wake control system's input specifications. In other embodiments,the output signal may be a digital data stream whose format isproprietary, or based on a standard such as Controller Area Network(CAN) or Ethernet, or another format as suits the specific application.From the foregoing, the present disclosure is not limited to anyspecific type of output signal and the type and format of that signalcan be updated as new requirements or industry standards appear.

In some embodiments the present invention's indication of hull draft canbe absolute, or relative to some offset either fixed or configurable, assuits the application. Units of measure can be based on standardsincluding but not limited to metric or Imperial, or even arbitrary unitsspecific to a given installation.

Furthermore, it is not necessary for pipe 5 to be comprised of actualpipe. A compartment of any type suitable to the specifics of theapplication may be used. However, many styles of pipe are inherentlycompatible with water-based installations, and the wide range offittings and other accessories available for piping products makes pipea straightforward choice in many embodiments.

The present disclosure supports significant mechanical adaptability. Forexample, the length and diameter of pipe 5 can be varied to suit thespecifics of a given application. A watercraft that naturally has deeperhull draft, or one that experiences greater variation in its draftduring operation, may benefit from a longer pipe 5 to insure that thetop of pipe 5 always remains above the surface of the surrounding water.The diameter of pipe 5, its wall thickness, its material, and otherattributes may also be varied based on installation or otherconsiderations. Different hull mounting styles may be accommodated. Thisability to be realized in a variety of form factors, using differingcomponents and materials, is a key advantage of the present disclosureand a significant advancement of the art.

In summary, the draft measuring system disclosed herein may compriseseveral alternative components. At a minimum the system includes a holethrough the hull of the wakeboat. The hole is positioned below theoperational waterline of the hull. Located within the hole is a fitting.The fitting may have any suitable profile on the exterior of the hullincluding but not limited to a mushroom style, a seacock style or aflush mount. An open pipe is attached to the fitting. Preferably, thepipe has a length greater than the greatest expected draft of the hull.Additionally, a shut-off valve is preferably included as an integralpart of the fitting, an integral part of the pipe or a separatecomponent located either between the pipe and the fitting or at the endof the pipe. Carried by the pipe is any one of or a combination of draftmeasuring systems. Suitable draft measuring systems include:

-   -   a float that measures the column of water within the pipe and        incorporates appropriate electronics to transmit a signal to the        wake control system;    -   optical emitters with compatible receptors, i.e. photodiodes or        phototransistors;    -   light sensors suitable for detecting a change in color within        the pipe;    -   light sensors suitable for monitoring a change in refraction of        light passing through the pipe;    -   an ultrasonic transducer positioned to monitor the water level        within the pipe;    -   a pressure transducer positioned within a cap attached to the        end of the pipe;    -   conductive strips carried by the exterior of the pipe and a        conversion module suitable to detect changes in capacitance        between the conductive strip resulting from changes in water        level within the pipe.        One skilled in the art will appreciate that the pipe used in        connection with the optical emitters and light sensors should be        optically transparent. Additionally, one skilled in the art will        recognize that the pipe used in connection with the conductive        strips must be non-conductive in order to permit the development        of a capacitive change between the strips. Finally, the draft        measuring system may optionally include a filtering mechanism to        eliminate changes in water volume within the pipe resulting from        external environmental conditions not associated with the        operation of the wakeboat, e.g. wind driven waves. Such        filtering mechanism may include a vent within a cap carried by        the open end of the pipe, a low pass mechanical filter, a        passive RC filter, an active amplifying filter and/or software        within the onboard wake control system.

The above described wake control system is particularly suited foraccurately reproducing wakes behind wakeboats. The method of using thewake control system begins with fitting a draft measuring system, asdescribed above, to the hull of a wakeboat. The wakeboat will have atleast one trim tab and at least one ballast tank controlled by theonboard wake control system. Typically, the wakeboat will have aplurality of trim tabs and ballast tanks. When a surfer is behind thewakeboat, the trim tabs and ballast tanks will be adjusted until thesurfer is satisfied with the wake. This first wake is then stored withinthe memory of the onboard wake control system. The stored data includesinformation produced by the draft measuring system which reflects thedraft of the wakeboat corresponding to the desired wake. As discussedabove, the draft measuring system includes a filtering mechanism whichenhances the accuracy of the stored wake by substantially eliminatingminor changes in draft resulting from the choppiness of the watersurface.

Upon completion of the surfer's turn behind the boat, the configurationof the wake will be available for future use. Subsequently, the surferreturns for another turn surfing the wake behind the wakeboat. However,onboard conditions such as passenger load, cargo load, passengerposition, cargo position or other onboard variables have changed. Theonboard wake control system will compensate for the changes in onboardvariables by recalling the stored profile including the data provided bythe draft measuring system. The onboard wake control system will thenadjust the trim tabs and ballast tanks to achieve an input from thedraft measuring system corresponding to the draft reflecting the storedfirst wake.

In compliance with the statute, embodiments of the disclosure have beendescribed in language more or less specific as to structural andmethodical features. It is to be understood, however, that the entireinvention is not limited to the specific features and/or embodimentsshown and/or described, since the disclosed embodiments comprise formsof putting the invention into effect.

What is claimed is:
 1. A wake control system for a wakeboat having ahull, said system comprising: at least one trim tab attached to saidwakeboat; at least one ballast tank carried by said wakeboat; the wakecontrol system capable of controlling the position of said at least onetrim tab and the fluid level within said at least one ballast tank andstoring data associated with the position of said at least one trim taband the fluid level within said at least one ballast tank; a fittingpositioned within an opening in the hull, said opening in the hulllocated below the operational waterline of the hull; an open pipeattached to said fitting, said open pipe providing fluid communicationbetween the exterior and interior of the hull; a draft measuring systemcarried by said pipe, said draft measuring system capable of generatinga signal representative of a wake profile for said hull within thewater, said signal received and stored by said wake control system. 2.The wake control system of claim 1, further comprising a shutoff valvepositioned between said open pipe and said fitting.
 3. The wake controlsystem of claim 1, wherein said draft measuring system is selected fromthe group consisting of: a float configured to measure a water columnwithin said pipe; an ultrasonic transducer position at the top of saidpipe to measure the water column within said pipe; a cap positioned ontop of said pipe, said cap carrying a pressure transducer.
 4. The wakecontrol system of claim 1, wherein said draft measuring system is anoptical sensor selected from the group of: at least one optical emitterpaired with at least one optical receptor; or, an optical emitter pairedwith at least one light sensor capable of detecting shifts in color orrefraction; wherein said pipe is optically transparent to light producedby said optical emitter.
 5. The wake control system of claim 1, furthercomprising a filter configured to minimize the effects of oscillationsof water level within said pipe.
 6. The wake control system of claim 5,wherein said filter is a vented cap covering the top of said pipe. 7.The wake control system of claim 5, wherein said filter is a mechanicallow pass filter that imposes a damping effect on the oscillations ofwater within said pipe.
 8. The wake control system of claim 5, whereinsaid draft measuring system is selected from the group consisting of: afloat configured to measure a water column within said pipe; anultrasonic transducer position at the top of said pipe to measure thewater column within said pipe; a cap positioned on top of said pipe,said cap carrying a pressure transducer; and, wherein said filter is anRC filter electrically coupled with said draft measuring system said RCfilter configured to filter the signal produced by said draft measuringsystem prior to said signal being received by said wake control system.9. The wake control system of claim 5, wherein said draft measuringsystem is selected from the group consisting of: a float configured tomeasure a water column within said pipe; an ultrasonic transducerposition at the top of said pipe to measure the water column within saidpipe; a cap positioned on top of said pipe, said cap carrying a pressuretransducer; and, wherein said filter is an active amplifying filterelectrically coupled with said draft measuring system said amplifyingfilter configured to filter the signal produced by said draft measuringsystem prior to said signal being received by said wake control system.10. The wake control system of claim 5, wherein said draft measuringsystem is selected from the group consisting of: a float configured tomeasure a water column within said pipe; an ultrasonic transducerposition at the top of said pipe to measure the water column within saidpipe; a cap positioned on top of said pipe, said cap carrying a pressuretransducer; and, wherein said wake control system includes filteringsoftware configured to cancel the effects of oscillations of water levelwithin said pipe.
 11. The wake control system of claim 5, wherein saiddraft measuring system is an optical sensor selected from the groupconsisting of: at least one optical emitter paired with at least oneoptical receptor; or, an optical emitter paired with at least one lightsensor capable of detecting shifts in color or refraction; wherein saidpipe is optically transparent to light produced by said optical emitter;and, wherein said filter is an RC filter electrically coupled with saiddraft measuring system said RC filter configured to filter the signalproduced by said draft measuring system prior to said signal beingreceived by said wake control system.
 12. The wake control system ofclaim 5, wherein said draft measuring system is an optical sensorselected from the group consisting of: at least one optical emitterpaired with at least one optical receptor; or, an optical emitter pairedwith at least one light sensor capable of detecting shifts in color orrefraction; wherein said pipe is optically transparent to light producedby said optical emitter; and, wherein said filter is an activeamplifying filter electrically coupled with said draft measuring systemsaid amplifying filter configured to filter the signal produced by saiddraft measuring system prior to said signal being received by said wakecontrol system.
 13. The wake control system of claim 5, wherein saiddraft measuring system is an optical sensor selected from the groupconsisting of: at least one optical emitter paired with at least oneoptical receptor; or, an optical emitter paired with at least one lightsensor capable of detecting shifts in color or refraction; wherein saidpipe is optically transparent to light produced by said optical emitter;and, wherein said wake control system includes filtering softwareconfigured to cancel the effects of oscillations of water level withinsaid pipe.
 14. A wake control system for a wakeboat having a hull, saidsystem comprising: at least one trim tab attached to said wakeboat; atleast one ballast tank carried by said wakeboat; the wake control systemcapable of controlling the position of said at least one trim tab andthe fluid level within said at least one ballast tank and storing dataassociated with the position of said at least one trim tab and the fluidlevel within said at least one ballast tank; a fitting positioned withinan opening in the hull, said opening in the hull located below theoperational waterline of the hull; an open pipe attached to saidfitting, said open pipe providing fluid communication between theexterior and interior of the hull; a cap positioned on top of said pipecarried by said fitting, said cap including a pressure transducerconfigured to measure air pressure within said pipe and capable ofgenerating a signal representative of the volume of water within saidpipe, said signal received and stored by said wake control system. 15.The wake control system of claim 14, further comprising a filterconfigured to minimize the effects of oscillations of water level withinsaid pipe.
 16. The wake control system of claim 15, wherein said filteris a vent within said cap.
 17. The wake control system of claim 15,wherein said filter is a mechanical low pass filter that imposes adamping effect on the oscillations of water within said pipe.
 18. Thewake control system of claim 15, wherein said filter is an RC filterelectrically coupled with said pressure transducer said RC filterconfigured to filter the signal produced by said pressure transducerprior to said signal being received by said wake control system.
 19. Thewake control system of claim 15, wherein said filter is an activeamplifying filter electrically coupled with said pressure transducersaid amplifying filter configured to filter the signal produced by saidpressure transducer prior to said signal being received by said wakecontrol system.
 20. The wake control system of claim 15, wherein saidwake control system includes filtering software configured to cancel theeffects of oscillations of water level within said pipe.
 21. A methodfor accurately reproducing a wake behind a wakeboat comprising:providing a wakeboat, said wakeboat having a hull fitted with a draftmeasuring system, at least one trim tab and at least one ballast tank,said at least one trim tab and at least one ballast tank controlled byan onboard wake control system; establishing a first wake behind saidwakeboat; measuring the draft of the hull using said draft measuringsystem, said draft measuring system generating a signal representativeof the measured draft; transmitting the signal representative of themeasured draft to said onboard wake control system; storing the value ofsaid measured draft in said onboard wake control system; changing atleast one of the following variables: number of passengers on saidwakeboat, the weight of all passengers on said wakeboat, the weight ofcargo on said wakeboat, the position of passengers on said wakeboat, theposition of cargo on said wakeboat, the angle of said at least one trimtab, the volume of liquid within said ballast tank; following the changein at least one of the variables, using said draft measuring system andsaid wake control system to reproduce said first wake.
 22. The method ofclaim 21, further comprising the step of filtering the signal generatedby draft measuring system to reduce the effect of water surfaceoscillations experienced by said draft measuring system.
 23. The methodof claim 21, wherein said draft measuring system comprises a fittingpositioned within a hole in the hull of said wakeboat, said hole beinglocated below the operational waterline of the hull, a pipe attached tosaid fitting, wherein said draft measuring system is a pressuretransducer carried by a vented cap carried by said pipe, wherein saidvent is configured to minimize oscillation of water within said pipe andsaid pressure transducer transmits a signal representative of the waterlevel within said pipe.